1. Field of the Invention
The present invention generally relates to texture mapping and more specifically to using extrapolation to compute texture map values for mipmaps that are not available.
2. Description of the Related Art
As the use of virtual memory has become more commonplace, the number of texture maps that can be accessed during graphics processing is no longer limited by the amount physical memory (local or system) where the texture maps are conventionally stored. Texture data can be stored on other storage resources, such as disk drives, CD drives, or even remote servers that have higher access latency than the physical memory. The texture data is retrieved as it is needed during processing. However, unlike retrieving texture data from the physical memory, the image quality is compromised during the time that the texture data is retrieved from the other storage resources.
It is particularly advantageous to store high resolution mipmaps of a texture on the other storage resources since those mipmaps are larger. Lower resolution mipmaps of the texture can be stored in the physical memory and used to produce images while the high resolution mipmaps are retrieved from the other storage resources. The result is that the texture map data appears blurry and then sharpens when the high resolution mipmaps become available in the physical memory.
Accordingly, what is needed in the art are systems and methods for improving the appearance of low resolution texture map data that is used while high resolution mipmaps are retrieved from a high latency storage resource. Additionally, it is desirable to smoothly transition from using extrapolated filtering to using interpolated filtering to produce the filtered texel values once a high resolution mipmap is retrieved from the high latency storage resource.